Python bindings taking too long to import

[Ornab]

Hi, 

I am new to NS-3 and was having some trouble with the Python bindings. After building  NS3 (I tried the Debug, Optimized, and Release profiles), when I try to run first.py, the program first builds NS3 and then freezes over, giving me results about 45-50 mins later. Using Print statements, I found that all the time is going in the import statements. Could this be an issue with the installation?

I am using NS3 on WSL with VSCode on an i5 machine with 8GB Ram. 

While configuring NS3, I get the message:

-- NS3_BINDINGS_INSTALL_DIR was not set. The python bindings won't be installed with ./ns3 install.

-- Set NS3_BINDINGS_INSTALL_DIR="/home/user/.local/lib/python3.10/site-packages" to install it to the default location.

But I'm not sure how do I set NS3_BINDINGS_INSTALL_DIR. Could this be the issue with the python bindings not working correctly?

Thanks in advance

[Gabriel Ferreira]

Building ns-3 takes a fair amount of time if you run

./ns3 configure --enable-examples --enable-tests && ./ns3 build

This is because you are building everything. If you run

./ns3 configure --enable-examplese --enable-python-bindings && ./ns3 run first.py

It will build only the libraries and then run the python script.

Loading the bindings can be pretty slow (from ns import ns). 

Not much I can do to speed it up. 

It runs an awful lot of stuff from cling and cppyy to build the bindings at runtime and make it available.

I haven't tried caching it to disk and then loading, but may be an option (like shader caches used in games, where you compile once and load later).

Regarding the NS3_BINDINGS_INSTALL_DIR. Don't touch that. It is meant for repackagers, not end-users.

[Ornab]

Got it, Thanks!